[Latin, In the matter of.] Concerning or regarding. The usual style for the name of a judicial proceeding having some item of property at the center of the dispute rather than adverse parties.
For example, proceedings to determine various claims to the assets of a bankrupt company could be called In re Klein Company, or In the matter of Klein Company.
Sometimes in re is used for a proceeding where one party makes an application to the court without necessarily charging an adversary. This may be done, for example, where a couple seeks to adopt a child or an adult wants to change his or her name.
Such actions may instead use the English translation "in the matter of" or the Latin words ex parte. The final decision on the style to be used for a particular lawsuit is usually made by the clerk of the court.